Method and apparatus for recording and reproducing mechanical vibrations



Dec. 24, 1935. R. L. A. NUBLAT 2,025,608

METHOD AND APPARATUS FOR RECORDING" AND REPRODUCING MECHANICAL VIBRATIONS Filed Aug. '7, 1931 2 Sheets-Sheet 1 Loud Speaker Amplifier Loud Speaker Secondary Winding R 9. Mfume Dec. 24, 1935. R- NUBLAT 2,025,608

METHOD AND APPARATUS FOR RECORDING AND REPRODUCING MECHANICAL VIBRATIONS Fig. 5

Filed Aug. 7, 1931 2 Sheets-Sheet 2 Patented Dec. 24, 1935 IMETHOD AND APPARATUS FOR RECORDING @ND ISEEPRODUCING MECHANICAL VIBRA- ION Ren Lon Adolphe Nublat, Le Parc Saint-Maur,

France, assignor to Socit a Responsabilit Limite: Socit dEtudes Pour LExploitation Des Brevets Nublat, Paris, France Application August 7, 1931, Serial No. 555,816 In France June 1, 1931 1 Claim.

The present invention has for main object a method for recording and reproducing mechanical vibrations and particularly sounds.

The said method is particularly characterized :in that:

1. Upon recording, the vibrations are used for tracing on a suitable carrier, by any known means, a groove presenting the following features:

(a) the groove constitutes a transparent zone on an opaque carrier, or an opaque zone on a transparent carrier;

(b) the width of the groove is constant at all points of the said groove;

'1 (c) this width is at least equal to the maximum variation of the amplitude of the recorded oscillations.

2. Upon reproduction, the groove thus obtained is caused to pass between a source of electromagnetic radiations (and particularly light) and a photo-electric cell sensitive to these radiations; a diaphragm is arranged in the path of the latter for restricting the bundle to a thin band perpendicular to the groove; finally, a portion of this bundle of constant width is intercepted so that the bundle falling upon the sensitive electrode of the photo-electric cell be always limited, on one side, by the intercepting surface and, on the other side, by one of the sinuousedges of the groove.

It will be understood that everything takes place exactly as if the phonogram was constituted, in the known manner, by a transparent (or opaque) zone limited, on one side, by a straight line and, on the other side, by the sinuosities of the phonogramic record.

But the method according to the invention has the advantage of allowing, owing to the constant width of the groove, a mechanical recording (without of course exclusing the possibility of photographic recording) and a reproduction by photo-electric means. Up to now, this result had never been obtained, and consequently constitutes a new technical effect. Besides, it presents many advantages.

It is known that mechanical recording of sounds is now very near perfection, but that the mechanical reproduction gives rise to diiiiculties. In fact, if it is desired to obtain a true reproduction of all the frequencies, it is not possible to avoid the noise produced by the friction of the stylus in the groove. Besides, this friction destroys the phonogram more or less rapidly.

Photo-electric reproduction avoids these inconveniences. On the contrary, photographic remeans therefore constitutes a considerable ad- I vantage.

But the invention allows moreover to obtain an amelioration in mechanical recording in itself. Up to now, this recording gave rise to a groove sinuous either in width or in depth. This groove was usually traced in a soft material and many operations were subsequently necessary for obtaining a phonogram capable of being reproduced. To avoid the long period of time necessary between the recording and reproducing operations and to be able to ascertain without delay the quality of the recording, it has been proposed to directly form the groove in a material sufficiently hard for allowing immediate reproduction. But it will be understood that the necessity of obtaining a certain relief causes in this case considerable passive resistances to appear which of course are to the detriment of the trueness of the recorded sounds.

According to the invention, mechanical recording is preferably effected on a transparent carrier coated with a thin opaque layer; the tool for tracing the groove has simply for function to remove this opaque layer for exposing the transparent layer. It will thus be understood that the mechanical action of the tool is reduced to the minimum, and that a perfect groove is obtained. This phonogram is immediately and indefinitely utilizable, since it is reproduced by photo-electric means. Finally, duplication of the initial phonogram is very easily obtained photographically by direct contact.

The invention includes in its scope all apparatus and applications of apparatus for carrying the present method into practice. These apparatus can be devised according to several forms of construction mainly differing from each other:

(a) by the nature of the carrier, which may be of any type, rigid or supple, and may be constimeans'can be those actually used in the art that is to say mechanical, electromagnetic, photographic or like means.

(d) by the means used for intercepting a portion of the bundle, thus limited, on one side, by the intercepting surface, on the other side, by one of the sinuous edges of the groove; these means may vary, if possible for instance:

-to arrange a mask between the light source and the film;

--to arrange this mask between the film and the photo-electric cell;

in the case of a strong photo-electric cell (selenium cell) or provided with an emitting cathode (vacuum, potassium, caesium or like cells), the sensitive electrode or the sensitive portion of the electrode can be made in such a manner that one of its sides be always placed within the bundle of light; the latter'is therefore limited by the said side of the electrode and by the sinuous edge of the groove;

in the same case, the electrode can be separated in two parts, each belonging to a definite circuit and both these circuits can be suitably connected to a single circuit of utilization if need be;

finally, these means can be combined together.

(6) By the fact that a suitable optical system is arranged between the film and the photo-electric cell so as to widen the bundle of light and to thus facilitate the arrangement of the mask concealing a portion of the said bundle.

The invention has also for object to provide means allowing to mechanically obtain a groove capable of giving, by projection on an ordinary photo-electric cell, a modulated current. These means consist in eliminating a portion of the V groove of constant width by the formation, by any suitable means, of a groove having rectilinear edges which overlaps the sinuous groove or is overlapped by the same, so as to obtain a resulting audible phonogrammic groove, limited on one side by one of the edges of the sinuous groove of constant width and, on the other side, by one of the edges of the rectilinear groove.

The rectilinear groove, which must have a width at least equal to one half the maximum variation of the amplitude of the oscillations recorded for the production of the sinuous groove of constant width, can be obtained either simultaneously with the production of the latter, or before, or after.

The elimination of the neutral portion of the sinuous groove can be effected by means of a fixed cutting stylus under which the film moves.

The invention has also for object a form of construction of a device in which a fixed cutting stylus, adapted to trace a rectilinear groove, is mounted on the framework of an electromagnetic apparatus actuating width and the rectilinear groove may be simultaneously formed and that the pressure on the film may be the same for each of the stylus.

The accompanying drawings illustrate, by way of example, a form of carrying the invention into practice.

Fig. 1 illustrates a portion of a talking kinematographic film recorded according to the invention.

Fig. 2 lsa diagrammatic view of a plant for the projection .of a film according to Fig. 1.

Fig. 3 illustrates an improved optical device according to the invention.

Fig. 4 shows a cathode of an improved photoelectric cell for obtaining the reading of a film recorded according to the invention.

Fig. 5 illustrates a photo-electric cell having a double cathode.

Fig. 6 is a side view of a device allowing the 5 simultaneous production of two grooves.

Fig. 7 is a front view of the same device.

Fig. 8 is an explanatory perspective view, on an enlarged scale, of the formation of the audible groove. 10

An original film adapted for phonogrammic recording according to the invention, comprises, in the form of construction illustrated in Fig. l, a transparent carrier l for a thin layer of opaque material 2 arranged on one side of the image, as indicated. According to the invention, on the film is traced a phonogrammic groove 3 of constant width by rising of the opaque layer by any suitable means and the width of which is at least equal to the maximum variation of the amplitude of the oscillations. An opaque phonogrammic tracing as previously defined might also be produced on a transparent film.

A phonogrammic tracing of uniform width, that is to say the edges of which always remain parallel, cannot produce, when'it is projected on a photo-electric cell, a modulated current necessary, after amplification, for operating a loud-' speaker. For modifying the surface of the spot of light sent on to the cathode of a photo-electric cell, it has been necessary, according to the invention, to intercept a portion of the beam of light in such a manner that the trace of this beam of light be always limited, on one side, by the intercepting surface, and, on the other side, by the 5 sinuous edge of the groove.

The initial phonogrammic groove, that is to say that visible on the film, must have, as indicated, a width at least equal to the variation of the maximum amplitudes of the recorded oscil- 40 lations, in order that the sinuous edges may always be respectively on one and the same side of the line of separation. The separation between the active and neutral portions of the beam of light is indicated by a dot and dash line in Fig. 1.

Fig. 2 diagrammatically illustrates a projection plant, in which a bundle of light is emitted by a suitable source 4, passes through a condenser 5 which directs it to a slot 6 provided in a member 1 behind which moves a film 8 recorded according to the invention. 7 The light beam which passes through it, is preferably widened in a special optical device 9 which subsequently projects it on to a photo-electric cell 10.

The beam of light can be either intercepted before it has reached the photo-electric cell, or it can be received as such by an improved photoelectric cell.

The interception of a portion of the light beam 0 can be effected in numerous ways which are obviously all included in the scope of the invention. V

A suitable mask can be arranged preferably as shown in Fig. 3, at the outlet end of the optical 5 device 9 which preferably increases the width of the light beam. This mask might be placed quite as well at any point of the light ray, from the source of light, to the photo-electric cell.

If the light beam is not intercepted, the cathode of the photo-electric cell is modified. Fig. 4 shows a cathode l I one half of which only (nonhatched portion) is sensitive to light. Strong selenium photo-electric cells, or provided with an emitting cathode, potassium or like cells, with or without gaseous atmosphere can be employed.

The hatched or neutral portion can also be eliminated; in this case, the cathode of the cell is displaced so that one of its vertical edges may be situated in the vertical axis of the cell and coincides with the separation line between the active portion (nonhatched portion) and the neutral portion (hatched portion) on which falls the light beam.

In a constructional modification, a photoelectric cell can consist in two emitting cathodes l l and I I placed in one and the same plane and electrically insulated in order to be each arranged in an independent circuit; these two circuits can react on a common circuit of utilization.

In case of a phonogrammic groove placed on the side and in order that it may not be projected on the screen with the kinematographic image, the film can be so made that a phonogrammic groove pervious to ultra-violet radiations be covered, after recording, with a thin layer opaque to light.

The invention has also for object the formation, on a film in which the image occupies the entire width, of a tracing produced by removal, by any suitable means, of a thin layer of a material allowing the passage of the light radiations for kinematographic projection, but stopping the nonvisible light rays, ultra-violet rays for instance. A film is thus obtained which allows the projection of images not reduced in width.

The reading of the sound'is effected in the manner previously set forth, either with a mask intercepting the ultra-violet rays passing through the phonogrammic groove, or with an improved photo-electric cell according to the invention.

A form of construction of a device allowing to simultaneously produce sinuous and rectilinear grooves for obtaining an audible phonogrammic groove by projection on an ordinary photoelectric cell, is illustrated in Figs. 6, '7, and 8.

A sinuous groove 3 of constant width, is mechanically obtained by means of a cutting stylus l2 which transversely vibrates under the action of an amplified modulated current, fed by a conductor [3 to the electromagnets (not shown) 01. a fixed apparatus l4, under which a film l to be recorded moves in the direction of the arrow 7.

The electromagnetic apparatus I4 is rigidly secured to an arm or support l6 through the medium of a keyed spindle H, but which allows the said apparatus to vertically move in translation by gravity and, if desired, under the action of a spring (not shown) the pressure of which can be adjusted by a screw l8. This arrangement allows to control the pressure of the stylus on the film. A stop screw l9 can neutralize the action of gravity by immobilizing the spindle I! in translation.

For obtaining a groove 20 having rectilinear edges which, according to one of the features of the invention must overlap the initial sinuous groove 3 for rendering it audible, a cutting stylus 2|, displaced relatively to the vibrating stylus I2, is secured by means of a screw 22 in a socket 23 attached to the framework of the apparatus I4 by screws 24.

This arrangement of two fixed and vibrating stylus on one and the same apparatus has for advantage of allowing to obtain, after adjustment of the position of each of the stylus, a pressure on the film which is equal for each of them, in order that the thin layers of material planed by the stylus be of equal thickness.

It is obvious that this arrangement of the stylus does not exclude from the invention the mounting of the fixed stylus on an independent support.

Likewise, the groove having rectilinear edges 20 might quite as well be formed before the sinuous groove 3, or after, simultaneously as in the preceding case, or on an apparatus independent of the recording apparatus.

As can be seen from Fig. 8, the fixed stylus 25 straddles one of the sinuous edges of the initial groove 3 and its width is greater than the maximum amplitude. of the oscillations recorded by the vibrating stylus E2, so that the resulting audible groove, that is to say a groove capable, by projection on any photo-electric cell, of producing a modulated current, be limited, on one side, by one of the sinuous edges of the initial groove, l2, and on the other side, by one of the rectilinear edges of the groove 20.

Substantially, the width of the cutting portion of the fixed stylus 2! is equal to that of the vibrating stylus E2.

The same result can be obtained by covering the neutral portion of the initial sinuous groove by means either of a liquid substance opaque to light,'applied in any suitable manner, or by sticking ribbon of suitable width and a suitable material.

What I claim as my invention and desire to secure by Letters Patent is:

A method of recording and reproducing sound by means of a transparent film having an opaque layer on a portion thereof consisting in tracing a reproduction of the vibrations of the sounds to so be recorded in said opaque layer to form a transparent sinuous band of constant width, projecting a beam of light on the transparent film, masking a portion of said beam to illuminate only onesinuous edge of said band, and translating the variable light passing through said band into sound vibrations.

RENE LEON ADOLPHE NUBLAT. 

